1. Field of the Invention
The present invention relates to a high-frequency (HF) cauterizing apparatus for medical treatment, with which incision of a living body tissue or hemostasis is performed by using a high-frequency current.
2. Description of the Related Art
In the field of surgical operations and medical treatment, an HF cauterizing apparatus has conventionally been used to perform incision or hemostasis by coagulation. In the HF cauterizing apparatus, a high-frequency (HF) medical treatment instrument is connected to a high-frequency (HF) power supply, and power or current applied from the HF medical treatment instrument to an affected part of a living body is controlled at an optimal level by a control device provided in the HF power supply. Thereby, desired medical treatment can be effected.
For example, U.S. Pat. No. 5,152,762, U.S. Pat. No. 5,108,398, U.S. Pat. No. 4,938,761 and U.S. Pat. No. 4,532,924 disclose means for controlling an output from a high-frequency power supply at an optimal level. Specifically, an output current from an active electrode connected to the HF power supply and a feedback current from a neutral electrode are sensed and compared, thereby indirectly detecting a leak current, detecting an impedance between an active-electrode-side output terminal and a neutral-electrode-side feedback terminal of the HF power supply, or sensing a temperature of heat applied to an affected tissue surface by providing a temperature sensor at an end portion of a bipolar electrode. On the basis of detected information, the value of a high-frequency output is controlled and optimal high-frequency outputs can be supplied to meet requirements of various surgical operations and medical treatment.
Suppose that an impedance between the output terminal of the HF power supply, on the one hand, and the electrode, living body, feedback current and feedback terminal of the HF power supply, on the other hand, is calculated by detecting an output current and output voltage within the HF power supply, and a high-frequency output is controlled so as to optimize a current density between a distal electrode portion of the treatment instrument and the affected part of the living body. In this case, however, there are various types of HF medical treatment instruments to be connected to the HF power supply, and the impedance of the HF medical treatment instruments in respect of high-frequency power or the area of the electrode portion in contact with the living body is not uniform. Consequently, variance occurs among detected output voltage values, output current values and impedance values, and the density of current applied to the affected part varies. As a result, optimal electric energy cannot be supplied. In other words, the density of current or power applied to the affected part cannot be controlled at a high-efficiency, optimal level. Thus, desired incision treatment or coagulation hemostasis treatment cannot be effected. In the case where the employed HF treatment instrument is changed or other affected part is treated consequently, even if the same operator performs the treatment with the same HF power supply, the state of incision or coagulation hemostasis will differ.
Besides, even if a temperature rise at the affected part is detected by a temperature sensor provided at a distal end portion of a bipolar electrode in order to control the coagulation state, noise may mix in a detection signal, depending on a noise level of high-frequency current output from the HF power supply itself. The noise degrades the detection precision. Consequently, it is difficult to control the high-frequency output at a desired level.
As has been described above, in most cases, when the HF cauterizing apparatus is used, the output power applied to the affected part and the output time are set by the operator by rule of thumb, for example, by viewing the affected part by the naked eye.
Under the circumstances, some means needs to be provided to exactly identify the types of many HF medical treatment instruments and feed a high-frequency output at optimal level to the treatment instruments. To provide such means is not easy in the case of the HF cauterizing apparatus with the above structure. In the above HF cauterizing apparatus, the treatment instrument is connected to the HF power supply, thereby constituting an electrically closed circuit comprising, e.g. a resistor, a capacitor, a coil, etc. which are separately provided on the treatment instrument side. By supplying weak high-frequency power to the closed circuit, a high-frequency resistance value of each treatment instrument is detected.
The reason why such weak high-frequency power is supplied in this case is that electric shock due to application of lower-frequency power is dangerous. In addition, if a resistance component is detected with low-frequency power, detection precision lowers. On the other hand, if DC current is supplied, noise of high-frequency power, etc. tends to occur. Thus, supply of DC current is technically undesirable. This being the case, weak high-frequency power is supplied. A detection value of the high-frequency resistance value is an analog value, which cannot be recognized by a control unit (including a CPU) which performs actual control. Accordingly, the control is switched by a control unit which does not include a CPU. Specifically, detected resistance values are compared by a comparison circuit, etc., and the output circuit is switched in accordance with the high/low level of the resistance values. However, in terms of precision, there is a limit to the technique of switching the control by detecting many treatment instruments by the comparison circuit. Forcible switching of the control in this case results in an abnormal increase in circuit scale and is practically difficult. In the case of the above HF cauterizing apparatus, at most a few types of medical treatment instruments can be identified.
On the other hand, when endoscopical medical treatment is performed by using a high-frequency cauterizing apparatus, a cord for equalizing the potential of a living body-side electrode of a high-frequency medical treatment instrument to the potential of an endoscope body is used. For example, this cord is a cord for feeding back a leak current from the endoscope body.
When HF medical treatment is performed by introducing a high-frequency treatment instrument such as an electric scalpel into the human body (or the patient) via an endoscope, a high-frequency current is let to flow from the instrument-side active electrode connected to a high-frequency cauterizing apparatus to the body-side counter electrode plate opposed to the active electrode. Thereby, an affected part located between the active electrode and counter electrode is incised or outflowing blood due to incision is coagulated and stopped. In this case, high-frequency current from the instrument-side active electrode leaks to a metallic portion of the endoscope body, and, as a result, the operator who touched the metallic portion may suffer a burn or a normal tissue may be cauterized. In order to avoid this from occurring, the leak current feedback cord, for example, is connected to a braid (a braid tube) provided over substantially the entire insertion portion of the endoscope, thereby equalizing the potential of the patient-side counter electrode to that of the endoscope body via the feedback cord. Thus, the high-frequency current leaking to the endoscope body (braid) is recovered and safety for the operator or patient is ensured.
A high-frequency cauterizing apparatus used in a surgical operation may have a spray coagulation function. According to the spray coagulation, a high voltage is generated and discharged to coagulate blood. The spray coagulation is very advantageous in that blood coagulation (hemostasis) is effected apart from the patient's bleeding part. Normally, blood is coagulated by thermal effect of high-frequency current by putting an electrode into contact with the bleeding part. In this case, however, blood may adhere to the electrode or when the electrode is removed after coagulation, the coagulated part adhered to the electrode may be separated from the body tissue and bleeding may occur once again. According to the spray coagulation, however, hemostasis can be effected apart form the bleeding part, and therefore the above drawbacks of the normal blood coagulation technique, wherein the electrode is put in contact with the bleeding part, can be avoided.
Needless to say, if endoscopical treatment can be performed by using the HF cauterizing apparatus having the spray coagulation function, convenience of the cauterizing apparatus will be enhanced. In other words, if the spray coagulation is effected and endoscopical HF medical treatment is performed with use of a single HF cauterizing apparatus, the cauterizing apparatus can be effectively used. However, if the HF cauterizing apparatus having the spray coagulation function is combined with the endoscope, the following problem will occur in an aspect of electrical safety.
In general, the HF cauterizing apparatus having the spray coagulation function has three modes: 1) an incision mode for incising a living body tissue by high-frequency current, 2) a spray coagulation mode for coagulating a bleeding part by electric discharge, and 3) a normal coagulation mode for coagulating blood with an electrode put in contact with a bleeding part. As is shown in FIG. 19, an output voltage (V) increases in proportion to an output power (W) in each mode. When the output power (W) is the same, the output voltages in the coagulation modes are higher than that in the incision mode, and the output voltage in the spray coagulation mode is higher than that in the normal coagulation mode. In general, electric discharge occurs more easily in the spray coagulation mode than in the normal coagulation, from the standpoint of waveforms.
Accordingly, if the spray coagulation function for coagulating blood of a bleeding part by generating high voltage and causing discharge is performed at the time of using the endoscope, there is a concern that an electric discharge occurs on the endoscope side. If the high-voltage discharge due to the spray coagulation acts on devices such as the endoscope, insulation breakage occurs in these devices and the operator may suffer a burn. In particular, the withstand voltage of endoscopes and HF treatment instruments for use in the field of internal treatment is lower than that of these devices for use in the field of surgical treatment. Besides, in general, it is not preferable, from the standpoint of withstand voltage, to use the spray coagulation function in the endoscopical treatment. Even if the aforementioned endoscope cord is used for the purpose of electrical safety, the problem due to high-voltage discharge of spray coagulation cannot be avoided.
More specifically, even if endoscopical treatment can be performed by using the HF cauterizing apparatus with the spray coagulation function, the aforementioned problem will occur if the spray coagulation function is erroneously performed. Thus, when the HF cauterizing apparatus with the spray coagulation function is combined with the endoscope in consideration of the aforementioned advantage, it is necessary to use the leak current feedback cord and ensure electrical safety.